Molecular survey of knockdown resistance to pyrethroids in human scabies mites

In vitro acaricidal activity of several natural products against ibex-derived Sarcoptes scabiei

In this study we analysed the effect of the temperature, diverse strains of Bacillus thuringiensis, Lysinibacillus sphaericus and nanoformulations with essential plant oils (EONP) on the survival of Sarcoptes scabiei mites derived from naturally-infested Iberian ibex (Capra pyrenaica). In general, mites maintained at 12ºC survived more than those maintained at 35ºC (40.7 hr and 31.2 hr, respectively). Mites with no treatment survived 27.6 h on average. Mites treated with B. thuringiensis serovar. konkukian and geranium EONP showed significant reduction in their survival. Despite the fact that these agents seem to be promising candidates for controlling sarcoptic mange in the field, further research is still needed to get stable, efficient and eco-friendly acaricides.

Spanish Academy of Dermatology and Venereology (AEDV) expert recommendations for the management of sexual transmitted parasitosis. Scabies, and pediculosis pubis

Sexually transmitted infections are communicable diseases where the pathogen is transmitted through sexual contact. The Sexually Transmitted Infections Working Group of the Spanish Academy of Dermatology and Venereology (AEDV) is engaged in the drafting of documents to guide dermatologists and health care personnel who treat Spanish patients with these infections. This document analyzes the epidemiological, clinical, therapeutic, and control characteristics of 2 sexually transmitted parasitosis: scabies due to Sarcoptes scabiei var. hominis, and pubic pediculosis due to Phthirus pubis. Both parasitoses share a sort of mixed spread through sexual and community transmission regardless of the route through which the infection was initially acquired. This specific feature creates particularities in the management and control of the infestation.

[Translated article] Spanish Academy of Dermatology and Venereology (AEDV) expert recommendations for the management of sexual transmitted parasitosis. Scabies, and pediculosis pubis

Sexually transmitted infections are communicable diseases where the pathogen is transmitted through sexual contact. The Sexually Transmitted Infections Working Group of the Spanish Academy of Dermatology and Venereology (AEDV) is engaged in the drafting of documents to guide dermatologists and health care personnel who treat Spanish patients with these infections. This document analyzes the epidemiological, clinical, therapeutic, and control characteristics of 2 sexually transmitted parasitosis: scabies due to Sarcoptes scabiei var. hominis, and pubic pediculosis due to Phthirus pubis. Both parasitoses share a sort of mixed spread through sexual and community transmission regardless of the route through which the infection was initially acquired. This specific feature creates particularities in the management and control of the infestation.

Failure of scabies treatment: a systematic review and meta-analysis

BACKGROUND

Treatment failure is considered to be an important factor in relation to the increase in scabies incidence over the last decade. However, the regional and temporal differences, in addition to the predictors of therapy failure, are unclear.

OBJECTIVES

We aimed to conduct a systematic review of the prevalence of treatment failure in patients with scabies and investigation of associated factors.

METHODS

We searched MEDLINE, EMBASE, CINAHL, Web of Science, Scopus, Global Health and the Cochrane Central Register of Controlled Trials from inception to August 2021 for randomized and quasi-randomized trials, in addition to observational studies that enrolled children or adults diagnosed with confirmed or clinical scabies treated with permethrin, ivermectin, crotamiton, benzyl benzoate, malathion, sulfur or lindane, and measured treatment failure or factors associated with treatment failure. We performed a random effects meta-analysis for all outcomes reported by at least two studies.

RESULTS

A total of 147 studies were eligible for inclusion in the systematic review. The overall prevalence of treatment failure was 15.2% [95% confidence interval (CI) 12.9-17.6; I2 = 95.3%, moderate-certainty evidence] with regional differences between World Health Organization regions (P = 0.003) being highest in the Western Pacific region (26.9%, 95% CI 14.5-41.2). Oral ivermectin (11.8%, 95% CI 8.4-15.4), topical ivermectin (9.3%, 95% CI 5.1-14.3) and permethrin (10.8%, 95% CI 7.5-14.5) had relatively lower failure prevalence compared with the overall prevalence. Failure prevalence was lower in patients treated with two doses of oral ivermectin (7.1%, 95% CI 3.1-12.3) compared with those treated with one dose (15.2%, 95% CI 10.8-20.2; P = 0.021). Overall and permethrin treatment failure prevalence in the included studies (1983-2021) increased by 0.27% and 0.58% per year, respectively. Only three studies conducted a multivariable risk factor analysis; no studies assessed resistance.

CONCLUSIONS

A second dose of ivermectin showed lower failure prevalence than single-dose ivermectin, which should be considered in all guidelines. The increase in treatment failure over time hints at decreasing mite susceptibility for several drugs, but reasons for failure are rarely assessed. Ideally, scabicide susceptibility testing should be implemented in future studies.

Detection of a knockdown mutation in the voltage-sensitive sodium channel associated with permethrin tolerance in Sarcoptes scabiei var. hominis mites

BACKGROUND

Increasing evidence has sparked a debate on the loss of sensitivity of scabies mites to conventional permethrin therapy. Mutations in the voltage-sensitive sodium channels (VSSC) were associated with knockdown resistance (kdr) in many arthropods, but have never been identified in Sarcoptes scabiei variatio (var.) hominis mites.

OBJECTIVES

To identify factors contributing to therapy failure.

METHODS

Sixty-seven mites were collected from 64 scabies-infested patients in Vienna, Austria, of whom 85.9% were refractory to prior permethrin-based treatments, and genotyped for the presence of nucleotide polymorphisms in Domain II of the VSSC, known to be associated with kdr. Information regarding previous antiscabietic therapies, decontamination procedures and possible re-infestations by contacts as well as the response to re-imposed therapies were obtained.

RESULTS

Sequence alignment comparisons revealed previously unidentified mutations in the coding region of Domain II of the VSSC. A novel A1663T transversion was detected in 97.0% of the mites, resulting in a non-synonymous substitution from methionine to leucine, M918L, a mutation known to confer kdr in other arthropods. In addition, a synonymous G1659A transition was identified in one mite, which otherwise showed a nucleotide sequence identical to the wild-type reference. No major inconsistencies were observed within the previous therapeutic and decontamination procedures, which could have accounted for the observed non-responsiveness to permethrin-based therapies. Subsequent cure of infestation was achieved in 65.6% of the participants, predominantly by combination therapies with topical permethrin and systemic ivermectin. However, in 14.6% of the cured cases, permethrin monotherapy sufficed for eradication of scabies, albeit in some cases prolonged exposure was necessary.

CONCLUSIONS

The kdr-associated M918L mutation in the VSSC gene has now emerged in S. scabiei var. hominis mites. Hence, loss of sensitivity to permethrin due to kdr-type resistance may be more prevalent than anticipated and may be decisive for the therapy responsiveness of scabies-infested patients.

A review of the molecular mechanisms of acaricide resistance in mites and ticks

The Arachnida subclass of Acari comprises many harmful pests that threaten agriculture as well as animal health, including herbivorous spider mites, the bee parasite Varroa, the poultry mite Dermanyssus and several species of ticks. Especially in agriculture, acaricides are often used intensively to minimize the damage they inflict, promoting the development of resistance. Beneficial predatory mites used in biological control are also subjected to acaricide selection in the field. The development and use of new genetic and genomic tools such as genome and transcriptome sequencing, bulked segregant analysis (QTL mapping), and reverse genetics via RNAi or CRISPR/Cas9, have greatly increased our understanding of the molecular genetic mechanisms of resistance in Acari, especially in the spider mite Tetranychus urticae which emerged as a model species. These new techniques allowed to uncover and validate new resistance mutations in a larger range of species. In addition, they provided an impetus to start elucidating more challenging questions on mechanisms of gene regulation of detoxification associated with resistance.

Diseases of Iberian ibex (Capra pyrenaica)

Iberian ibex (Capra pyrenaica) is an ecologically and economically relevant medium-sized emblematic mountain ungulate. Diseases participate in the population dynamics of the species as a regulating agent, but can also threaten the conservation and viability of vulnerable population units. Moreover, Iberian ibex can also be a carrier or even a reservoir of pathogens shared with domestic animals and/or humans, being therefore a concern for livestock and public health. The objective of this review is to compile the currently available knowledge on (1) diseases of Iberian ibex, presented according to their relevance on the health and demography of free-ranging populations; (2) diseases subjected to heath surveillance plans; (3) other diseases reported in the species; and (4) diseases with particular relevance in captive Iberian ibex populations. The systematic review of all the information on diseases affecting the species unveils unpublished reports, scientific communications in meetings, and scientific articles, allowing the first comprehensive compilation of Iberian ibex diseases. This review identifies the gaps in knowledge regarding pathogenesis, immune response, diagnostic methods, treatment, and management of diseases in Iberian ibex, providing a base for future research. Moreover, this challenges wildlife and livestock disease and wildlife population managers to assess the priorities and policies currently implemented in Iberian ibex health surveillance and monitoring and disease management.

Is there a really resistance to scabies treatment with permethrin? In vitro killing activity of permethrin on Sarcoptes scabiei from patients with resistant scabies

Recently, there have been increased scabies infestations but many patients do not respond to treatment. Clinicians are hesitant to use permethrin despite the fact that treatment failure may be due to noncompliance with the treatment rather than permethrin resistance. We aimed to investigate the permethrin resistance of mites collected from patients who have endured scabies for at least 3 months despite permethrin treatment. Parasites in patients who had scabies for at least 3 months despite permethrin treatment were collected. Only parasites that were not damaged during sampling, not fragmented and had full motion were included. Parasites were divided into four groups, each with 15 parasites. Immersion oil was dripped on the control group and 5%, 7%, and 10% permethrin was added to the study groups. The responses of the parasites to the applied agents were examined using a digital microscope. All solutions, except the control group, killed the scabies mite. The mean survival time (ST) in the 5%, 7%, and 10% permethrin groups was 360 ± 33.2, 340 ± 31.4, and 320 ± 30.2 min, respectively. There was no statistically significant difference in the mean ST in the permethrin groups. The mean ST in the control group was 46 ± 1.5 h. The mean ST difference between the control and permethrin-treated groups was significant (p = 0.03). There was no resistance to permethrin, which should maintain its place as first line treatment of scabies. Treatment noncompliance, rather than permethrin resistance, seems to be the underlying factor in the chronicity of scabies.

Scabies: Epidemiology, Diagnosis, and Treatment

BACKGROUND

Scabies is a skin infestation whose incidence is apparently rising.

METHODS

This review is based on pertinent articles retrieved by a selective search of PubMed on diagnosis and treatment strategies.

RESULTS

Thread-like papules (burrows), new, intense pruritus, and dermatitis guide the suspected diagnosis which is confirmed by the microscopic or dermatoscopic demonstration of scabies mites. The first line therapy is topical application of permethrin, in accordance with the current recommendations for its use. Other treatment options include systemic ivermectin and topical crotamiton or benzyl benzoate. A combination of permethrin and ivermectin is used to treat otherwise intractable cases and is generally indicated for the treatment of crusted scabies. Known causes of treatment failure include improper application of the external agents, failure of repeated treatment with ivermectin, incomplete decontamination of furnishings and clothes, failure to simultaneously treat contact persons, absence of written documents explaining treatment modalities, and the patient's belonging to a risk group. Even though there has not yet been any direct proof of resistance of scabies mites to permethrin, there is a rising number of welldocumented cases of poor response to this agent. Moxidectin is a new substance now undergoing clinical testing.

CONCLUSION

Treatment of scabies according to the guidelines and the additional recommendations reported here should result in effective curing, even in cases that are thought to be intractable.

Comment on: "The treatment of sarcoptic mange in wildlife: a systematic review"

This letter comments on the article “The treatment of sarcoptic mange in wildlife: a systematic review” published in Parasites & Vectors 2019, 12:99, and discusses the limitations in the use of endectocides for scabies control in free-ranging wildlife. The ecological impact and drug resistance to ivermectin are also discussed. In our view, scabies control in free-ranging wildlife should be based preferably on population management measures, and whether to apply individual treatments to free-ranging populations should be considered very carefully and avoided where not absolutely warranted.

[Scabies therapy in Germany : Results of a nationwide survey with a special focus on the efficacy of first-line therapy with permethrin]

BACKGROUND

According to the current scabies guideline, topical treatment with permethrin 5% cream is the first-line therapy of common scabies in Germany. However, in the course of growing incidence of scabies in recent years there have been increasing numbers of reports of reduced efficacy in standard therapy.

OBJECTIVE

To establish a better understanding for the efficacy of scabies therapy under practice conditions, a survey focusing on the first-line therapy with permethrin was conducted in dermatological hospitals, outpatient clinics and dermatology practices.

METHODS

The postal survey addressed all dermatologically active physicians in Germany and queried diagnostic methods, the individual initial treatment, the estimated efficacy of permethrin therapy, the frequency and reasons for therapy failures under permethrin and the therapeutic approach in case of failure of the initial therapy.

RESULTS

The efficacy of permethrin was rated with 73% by 187 physicians. About 74% reported to treat initially with 5% permethrin cream. The most common reasons identified for treatment failure were application errors, lack of compliance and inadequate hygiene measures. Suspected diminished efficacy or development of resistance against permethrin and re-infestations were also mentioned. In the case of ineffectiveness of initial therapy, most clinicians opt for oral ivermectin, a repetition of permethrin therapy or a combination of both.

CONCLUSION

Although there are localized reports of decreased effectiveness of permethrin therapy, results of this survey point towards a persisting high efficacy of first-line standard treatment of scabies with permethrin 5% cream in Germany.

The in vitro antibacterial effect of permethrin and formaldehyde on Staphylococcus aureus

Antibiotic‐resistant strains of bacteria such as methicillin‐resistant Staphylococcus aureus are a threat to human health, and effective treatment options against them are needed. This study aimed to determine whether the insecticide permethrin was capable of inhibiting the growth of S. aureus or if some other component of a permethrin cream was responsible for a decrease in scabies associated bacterial infection previously observed. Ten S. aureus strains were grown in the presence of permethrin and formaldehyde both alone and in combination with percent inhibition determined by viable counts. Also, a time‐kill assay was conducted on S. aureus exposed to the same conditions. Finally, the morphology of S. aureus grown in the presence of permethrin was examined by scanning electron microscopy. Bacterial inhibition by permethrin ranged from 0% to 41% whereas inhibition by formaldehyde was 100%. The time‐kill curves of permethrin exposed cells were very similar to the positive growth control while the formaldehyde and combination exposure showed complete inhibition even at the 0‐hr time point. The scanning electron micrographs of permethrin grown S. aureus showed healthy cocci cells with no sign of cell damage. Our results show that permethrin is not capable of inhibiting the growth of bacteria enough for it to be termed bactericidal. Formaldehyde is a known antiseptic and therefore was responsible for the antibacterial effect observed after the use of permethrin cream.

Formaldehyde as an alternative to antibiotics for treatment of refractory impetigo and other infectious skin diseases

Introduction: Antibiotic-resistant strains of bacteria are an increasing problem in hospitals and in the community. This has resulted in bacterial infections such as impetigo becoming difficult to treat. Alternative treatment options are needed. Areas covered: In this paper, a past study that assessed the health burden of scabies in North Queensland is described and from it, the potential for formaldehyde as an alternative antimicrobial treatment is discussed. In doing so, antibiotic resistance, impetigo, permethrin, and formaldehyde are introduced and the current understanding and limitations of the effects of formaldehyde on humans are outlined. The limited cases of formaldehyde resistance in bacteria are also discussed. Expert opinion: Formaldehyde is currently used as a preservative in cosmetics and medicinal creams due to its antibacterial activity. It, therefore, has the potential to be used as an alternative antibacterial treatment for infections with antibiotic-resistant bacteria. The harmful side effects of airborne formaldehyde and exposure in allergic individuals have been extensively studied. Significantly less research has been conducted on formaldehyde skin contact in healthy individuals. If formaldehyde is safe for topical use in humans, it has the potential to assist with combating antibiotic resistance.

Increase of scabies in Germany and development of resistant mites? Evidence and consequences

Scabies has been diagnosed surprisingly frequently in Germany in recent years, and the use of acaricides has risen markedly. Present figures indicate an increase in the prevalence/incidence of scabies, but do not prove or quantify it for the following reasons: (a) scabies is not a notifiable disease in Germany; (b) the diagnosis is not always confirmed lege artis by means of light microscopy or dermatoscopy (which may lead to a comparatively high proportion of false‐positive diagnoses due to the low overall prevalence of scabies); (c) repeated treatments of the same patient and treatment of contact persons are included in the total number of prescriptions. Therefore, there are no valid data on disease occurrence, either in the current situation or from previous periods. Observations of ineffective treatment with permethrin have led to speculations that Sarcoptes mites are developing resistance to this drug. However, there is little evidence for this assumption. We discuss risk groups (children, elderly people in need of care, migrant health personnel in nursing institutions, refugees, sexually active young adults) and evaluate their possible contribution, albeit in the absence of evidence. None of the groups would be solely responsible for an increased frequency. We have compiled recommendations on how the management of scabies could be improved, and present a way of differentiating permethrin resistance from application errors and/or lack of compliance. The goal is to solve the epidemiological and parasitological questions mentioned above.

Global output of research on epidermal parasitic skin diseases from 1967 to 2017

Background

Epidermal parasitic skin diseases (EPSD) occur in most countries and cause a considerable health and economic burden, particularly in the tropics and subtropics. The aim of this study was to assess and analyse peer-reviewed literature on EPSD in humans. The results of this study serve as an indicator of the extent the scientific community, health authorities, and international health agencies interact with EPSD as a health problem that is commonly associated with poverty and poor hygiene.

Methods

A bibliometric analysis methodology was used. The Scopus database was used to retrieve documents about EPSD for the study period (1967–2017). The study focused on scabies, tungiasis, pediculosis, hookworm-related cutaneous larva migrans (HrCLM), myiasis, and cutaneous strongyloidiasis. Documents that specifically and explicitly discuss EPSD in animals, aquatic organisms, and birds were excluded.

Results

In total, 4186 documents were retrieved. A fluctuated growth of publications on EPSD in the past five decades was found. The retrieved documents received 43 301 citations, an average of 10.3 citations per article and an h-index of 74. The keywords “scabies” and was the most commonly encountered keyword followed by the keywords “head lice” and “pediculosis”. The most active journal involved in publishing articles on EPSD was the International Journal of Dermatology (164; 3.9%). Researchers from 93 different countries published the retrieved articles. The USA led with 735 (17.6%) documents, followed by the UK (274; 6.5%), and Germany (259; 6.2%). In terms of institutions, the Charité – Universitätsmedizin Berlin in Germany was the most active in this field with 78 (1.9%) publications, followed by the Universidade Federal do Ceará in Brazil with 52 (1.2%) publications.

Conclusions

Research on scabies and pediculosis dominated the field of EPSD research to the expense of tungiasis, HrCLM, myiasis, and cutaneous strongyloidiasis. There was an underrepresentation of literature from the tropics and subtropics despite EPSD being common in these areas. This could possibly be explained by the presence of limited number of non-English journals in the Scopus database. International research collaborations and research networking should be strengthened to help advance and prioritize research on EPSD.

Electronic supplementary material

The online version of this article (10.1186/s40249-018-0456-x) contains supplementary material, which is available to authorized users.

Serodiagnostic Potential of Alpha-Enolase From Sarcoptes scabiei and Its Possible Role in Host-Mite Interactions

Infestation of the epidermis with the highly contagious ectoparasite, Sarcoptes scabiei, causes scabies, which is characterized by intense itching, pruritus, and secondary infection. This condition affects humans, livestock, and wildlife worldwide, incurring large economic losses and reducing the quality of human life. In the present study, we cloned the alpha-enolase, a key enzyme in the glycolytic and gluconeogenesis pathways, from S. scabiei var. cuniculi, characterized it and produced soluble recombinant enolase protein (rSsc-eno). We determined the localization of Ssc-eno in isolated mites and mites in lesioned skin. The results showed that native enolase was intensely localized in the tegument of the mouthparts, the entire legs, and the whole mites' body, as well as in the gut and reproduction system. Interestingly, we found that native enolase was widely distributed in mites in lesioned skin, with obvious high protein intensity compared with isolated mites. Building on good immunoreactivity, an indirect enzyme-linked immunosorbent assay (ELISA) based on rSsc-eno showed 92% sensitivity and 95.8% specificity, compared with other indirect ELISA in this study, rSsc-eno based ELISA is better in detecting scabies in rabbits. Besides, this method can detect S. scabiei infection as early as 1 week post infection. Compared with other detection methods, such as traditional microscopic examination and recently published universal conventional PCR, rSsc-eno ELISA was more effective to detect early infection in rabbits. Additionally, in vitro incubation experiments demonstrated the concentration-dependent acaricidal activity of rabbit anti-rSsc-eno sera against larval mites, suggested its potential as a vaccine candidate.

European guideline for the management of scabies

Scabies is caused by Sarcoptes scabiei var. hominis. The disease can be sexually transmitted. Patients' main complaint is nocturnal itch. Disseminated, excoriated, erythematous papules are usually seen on the anterior trunk and limbs. Crusted scabies occurs in immunocompromised hosts and may be associated with reduced or absent pruritus. Recommended treatments are permethrin 5% cream, oral ivermectin and benzyl benzoate 25% lotion. Alternative treatments are malathion 0.5% aqueous lotion, ivermectin 1% lotion and sulphur 6-33% cream, ointment or lotion. Crusted scabies therapy requires a topical scabicide and oral ivermectin. Mass treatment of large populations with endemic disease can be performed with a single dose of ivermectin (200 micrograms/kg of bodyweight). Partner management needs a look-back period of 2 months. Screening for other STI is recommended. Patients and close contacts should avoid sexual contact until completion of treatment and should strictly observe personal hygiene rules when living in crowded spaces. Written information should be provided to suspected cases.

Are humans the initial source of canine mange?

Background

Scabies, or mange as it is called in animals, is an ectoparasitic contagious infestation caused by the mite Sarcoptes scabiei. Sarcoptic mange is an important veterinary disease leading to significant morbidity and mortality in wild and domestic animals. A widely accepted hypothesis, though never substantiated by factual data, suggests that humans were the initial source of the animal contamination. In this study we performed phylogenetic analyses of populations of S. scabiei from humans and from canids to validate or not the hypothesis of a human origin of the mites infecting domestic dogs.

Methods

Mites from dogs and foxes were obtained from three French sites and from other countries. A part of cytochrome c oxidase subunit 1 (cox1) gene was amplified and directly sequenced. Other sequences corresponding to mites from humans, raccoon dogs, foxes, jackal and dogs from various geographical areas were retrieved from GenBank. Phylogenetic analyses were performed using the Otodectes cynotis cox1 sequence as outgroup. Maximum Likelihood and Bayesian Inference analysis approaches were used. To visualize the relationship between the haplotypes, a median joining haplotype network was constructed using Network v4.6 according to host.

Results

Twenty-one haplotypes were observed among mites collected from five different host species, including humans and canids from nine geographical areas. The phylogenetic trees based on Maximum Likelihood and Bayesian Inference analyses showed similar topologies with few differences in node support values. The results were not consistent with a human origin of S. scabiei mites in dogs and, on the contrary, did not exclude the opposite hypothesis of a host switch from dogs to humans.

Conclusions

Phylogenetic relatedness may have an impact in terms of epidemiological control strategy. Our results and other recent studies suggest to re-evaluate the level of transmission between domestic dogs and humans.

Therapeutic Potential of Tea Tree Oil for Scabies

Globally, scabies affects more than 130 million people at any time. In the developed world, outbreaks in health institutions and vulnerable communities result in a significant economic burden. A review of the literature demonstrates the emergence of resistance toward classical scabicidal treatments and the lack of effectiveness of currently available scabicides in reducing the inflammatory skin reactions and pyodermal progression that occurs in predisposed patient cohorts. Tea tree oil (TTO) has demonstrated promising acaricidal effects against scabies mites in vitro and has also been successfully used as an adjuvant topical medication for the treatment of crusted scabies, including cases that did not respond to standard treatments. Emerging acaricide resistance threatens the future usefulness of currently used gold standard treatments (oral ivermectin and topical permethrin) for scabies. The imminent development of new chemical entities is doubtful. The cumulative acaricidal, antibacterial, antipruritic, anti-inflammatory, and wound healing effects of TTO may have the potential to successfully reduce the burden of scabies infection and the associated bacterial complications. This review summarizes current knowledge on the use of TTO for the treatment of scabies. On the strength of existing data for TTO, larger scale, randomized controlled clinical trials are warranted.

Understanding the biology and control of the poultry red mite Dermanyssus gallinae: a review

Dermanyssus gallinae, the poultry red mite (PRM), is a blood-feeding ectoparasite capable of causing pathology in birds, amongst other animals. It is an increasingly important pathogen in egg layers and is responsible for substantial economic losses to the poultry industry worldwide. Even though PRM poses a serious problem, very little is known about the basic biology of the mite. Here we review the current body of literature describing red mite biology and discuss how this has been, or could be, used to develop methods to control PRM infestations. We focus primarily on the PRM digestive system, salivary glands, nervous system and exoskeleton and also explore areas of PRM biology which have to date received little or no study but have the potential to offer new control targets.

Investigation of dimethyl sulfide formation during GC analysis of permethrin API: study of the reaction kinetics and estimation of the activation energy of the reaction

Dimethyl sulfide was formed via a reaction between dimethyl sulfoxide and 3-phenoxylbenzyl chloride during gas chromatography analysis of the active pharmaceutical ingredient permethrin (PMN). The kinetics and the activation energy of the reaction are presented herein.

Sarcoptes scabiei mites in humans are distributed into three genetically distinct clades

Scabies is an ectoparasitic infestation caused by the mite Sarcoptes scabiei. Currently, S. scabiei is taxonomically divided into different varieties on the basis of host origin. Genetics-based research on scabies has been conducted, but the data on genetic diversity of populations of this mite in humans in Europe are lacking. We evaluated the genetic diversity of populations of S. scabiei. A large series of mites obtained from humans in France and the data of mites from various hosts and geographical areas retrieved from GenBank were included to investigate whether mites are divided into distinct populations. The study of cytochrome c oxidase subunit 1 gene polymorphisms were found to be best suited for phylogenetic analysis. S. scabiei mites were distributed into three genetically distinct clades, with most mites clustering in clades B and C. The Fst value and the Nm value calculated for mites included in clades B and C indicated a strong population structure and a very low gene flow between mites of those clades. The results of the present study not only support the rejection of the hypothesis of panmixia for S. scabiei in humans but also suggest that mites belonging to different clades are genetically isolated. Moreover, the results suggest that the subdivision of S. scabies in varieties according to animal or human hosts is not warranted. In conclusion, S. scabiei mites in humans do not constitute a homogeneous population. Further investigations are now required to assess whether different clinical forms of scabies are associated with particular haplotypes or clades.

Efficacy assessment of biocides or repellents for the control of Sarcoptes scabiei in the environment

BACKGROUND

Sarcoptes scabiei infection is a contagious disease affecting both humans and animals. The transmission occurs either by direct contact or from the environment where mites could survive several days remaining infective. The number of products available for environmental control of S. scabiei is very limited. The objective of the present study was to assess the efficacy of biocides or repellents against S. scabiei var suis.

METHODS

Tested products included pyrethroids: permethrin, esdepallethrin and bioresmethrin, bifenthrin, cypermethrin and imiprothrin, cyfluthrin, tetramethrin and sumithrin. We also tested repellents: DEET, icaridin and IR3535. Sarcoptes scabiei var suis mites were collected from experimentally-infected pigs. For each test, 20 live mites of all motile stages were placed in a plastic Petri dish and sprayed uniformly by each product. Control mites were sprayed by distilled water. The study was performed in triplicate under room conditions and the mites were inspected under a stereomicroscope at intervals (5, 10, 15, 20, 25, 30, 40, 50, 60 min, 2, 3, 4, 5 and 24 h) after exposure to the products.

RESULTS

All the products, except the combination of tetramethrin and sumithrin (A-PAR), were able to kill all mites within 24 h. The median survival time was 50 ± 30.4 min, 120 ± 309 min, 10 ± 5.9 min, 40 ± 36.8 min, 15 ± 7.3 min, 180 ± 417 min and 1440 ± 600 min when mites were exposed to permethrin 4 %, permethrin 0.6%, esdepallethrin and bioresmethrin, bifenthrin, cypermethrin and imiprothrin, cyfluthrin, tetramethrin and sumithrin, respectively. The median survival time was 20 ± 6.5 min, 15 ± 4.3 min, 30 ± 42.1 min and 15 ± 4.9 min for DEET 25, DEET 50, icaridin 20 and IR3535 20%, respectively.

CONCLUSIONS

The results of the present study could support evidence-based use of biocides and repellents in households, hospitals and farms.

Wombats acquired scabies from humans and/or dogs from outside Australia

According to previous studies, Sarcoptes mites of wombats were relatively recently introduced into Australia by colonizers and/or their dogs. However, that affirmation has been called into question due to apparent flaws in the design of the phylogenetic studies. With the aim of providing a definitive answer to this question, a part of the mitochondrial gene coding for 12S rRNA of S. scabiei mites from 23 humans and one dog collected in France was sequenced and a phylogenetic analysis including the sequences previously deposited in Genbank was performed. Phylogenetic analysis did not show host segregation or geographical isolation of the mites. Conversely, the present work suggested that mange in wombats is indeed due to the introduction of S. scabiei into Australia by immigrating individuals and/or their companion animals.

Parasitic mites of medical and veterinary importance--is there a common research agenda?

There are an estimated 0.5-1 million mite species on earth. Among the many mites that are known to affect humans and animals, only a subset are parasitic but these can cause significant disease. We aim here to provide an overview of the most recent work in this field in order to identify common biological features of these parasites and to inform common strategies for future research. There is a critical need for diagnostic tools to allow for better surveillance and for drugs tailored specifically to the respective parasites. Multi-'omics' approaches represent a logical and timely strategy to identify the appropriate mite molecules. Recent advances in sequencing technology enable us to generate de novo genome sequence data, even from limited DNA resources. Consequently, the field of mite genomics has recently emerged and will now rapidly expand, which is a particular advantage for parasitic mites that cannot be cultured in vitro. Investigations of the microbiota associated with mites will elucidate the link between parasites and pathogens, and define the role of the mite in transmission and pathogenesis. The databases generated will provide the crucial knowledge essential to design novel diagnostic tools, control measures, prophylaxes, drugs and immunotherapies against the mites and associated secondary infections.